The present invention relates to a lifting device and to a method of operating that lifting device. More specifically, the lifting device has a support and a working means mounted on the support for treating a surface. A pressure mechanism is arranged between the support and the working means and provides a contact and engaging force on the working means.
U.S. Pat. No. 4,286,417 discloses a device with a movable boom for supporting the device as it treats a surface. A device for cleaning the surfaces of objects having extensive surface areas with a movable blasting jet basket or cage is disclosed in DE 36 29 623 C2. In this case, one of more jet nozzles of a sand blasting apparatus, as disclosed in AT E 151 678 T1, are located in the blasting jet basket or cage for dust-free application of the blasting on surfaces.
EP 0 511 636 A1 discloses a device for positioning and guiding a tool, for example a cleaning tool for the aircraft. The alignment of the working means is performed by sensor-controlled stepping motors mounted on pivotal support arms articulated with one another. A similar arrangement of support arms, arranged one behind the other and articulated together and pivotally powered by a motor is disclosed in WO 83/03071.
EP 0 665 085 A1 discloses a device for working a surface in which the working means is engaged by magnetic force on the surface to be worked. The permanent magnets applying the magnetic force in this case are arranged on a support device for the working means.
DE 93 10 642 U1 discloses a surface blasting device having two removal suction openings offset from one another arranged in the working basket or cage. Within the working basket or cage baffle are found.
The lift platform includes an undercarriage which is customarily power-driven. An upper carrying chassis, rotatable around a perpendicular axis, is mounted on the undercarriage. On the upper carrying chassis, an overhand beam can pivot around a horizontal axis. The overhand beam is telescopically extensible, and its end more distant from the upper carrying chassis has a working means, a work platform or a working basket or cage, for example a blasting jet basket or cage.
The device can also incorporate, for example, a shearing device platform or a stamp, ram or piston platform. Its end adjacent to the surface to be worked supports a platform corresponding to the end of the overhang beam carrying the working means. In this embodiment, the device is preferably mounted on a movable undercarriage, especially on a movable undercarriage having a completely insertable steering control with an articulation angle of at least 90xc2x0, preferably on both sides or in both directions. Thus, by moving the platform during the overhead blasting procedure, the working means is brought into contact with the surface to be worked, while the forward thrust and the parallel displacement are carried out essentially by displacement of the platform. The engagement attained by displacement or positioning of the platform occurs during the blasting to the side, whereas the forward thrust can be executed especially by lifting and lowering of the platform. The working of the surface in terms of parallel movement in turn is performed especially by moving the platform forward. A multiply-articulated overhang beam can come into consideration as another alternative to the lifting platform, which multiply-articulated overhang beam customarily provides redundant spatial coverage by its mechanical means involving a number of articulations.
For certain purposes, for example involving the use of the lifting platform as the blasting tool itself, the working means is engaged directly on the surface to be worked. Prom the point of view of industrial safety, and for ecological and economical reasons, the working means must have the capacity to be engaged on the surface to be worked in such a manner that it engages the surface within a peripheral seal. For this purpose for example single-or double-row brush seals, a vacuum seal or a seal supported by magnetic force, as known from DE 29 04 093 A1, come into consideration.
In the case of a known lifting platform, the working means is engaged or pressed onto the surface to be worked through a pivot moment of the upper carrying chassis. The chassis is pivotal around the perpendicular axis relative to the undercarriage, or by means of sensor-controlled, multiple-axle drive systems engaging directly on the working means. This arrangement incorporates the drawback that either the contact and engagement force is not precisely adjustable and controllable because the total mass and bulk weight of the upper carrying chassis, the overhang beam and the working basket or cage must all be pivoted by the pivot movement, or the sensor-controlled drive systems are susceptible to interference in the area of the working means. Neither the required sealing between working means and surface to be worked nor the required service life of the lifting platform is guaranteed. Therefore, with the known lifting platform, the operational procedures on sensitive surfaces, such as for example for cleaning or application of varnish or paint to aircraft surfaces, cannot be carried out.
Objects of the present invention are to provide a device for the working of a surface, especially a lifting platform, which platform also has a long service life and provides an adjustable contact and engagement force controlled with a high degree of constancy.
Objects of the present invention also include a method for the operation of such a lifting platform. The method is to guarantee particularly the covering of a predeterminable path on a surface having high maintenance requirements, wherein the working means is in constant contact with the surface to be worked.
The foregoing objects are attained through a lifting device for treating a work surface comprising a support and a working means for engaging the work surface mounted on the support. Pressure means, arranged between the support and the working means, provides a contact and engagement force on the working means. A suspension suspends the working means to more freely about two angularly oriented axes. The pressure means engages the suspension.
The foregoing objects are also obtained by a method of operating a lifting device, comprising the steps of contacting and engaging a working means on a surface to be treated by a pressure means arranged between the working means and a support on which the working means is mounted, displacing said working means along a predetermined path, and compensating for modifications of distances between the working means and the surface to be treated resulting from displacement of the working means along the predetermined path by a suspension engaging the pressure means and suspending the working means to move freely about two angularly oriented axes.
By the working means being suspended on the suspension arrangement, it is universally movable and can move freely about two axes forming preferably a right angle. Additionally, the means for supplying the contact and engagement force engages on the suspension arrangement, without any need for multiple-axle, sensor-controlled and breakdown-susceptible drive devices. Thus, a secure contact of the working means with the surface to be worked is guaranteed. The contact and engagement of the working means on the surface to be worked is executed by means of an independent single-axle control and regulation, and particularly with continuous force.
The suspension is preferably in the form of a fork-like suspension arrangement for the bellxe2x80x94or basket-shaped working means. The shaft of the fork-like suspension is suspended universally rotatable around its longitudinal axis, for example by means of a tapered or conical roller bearing. With suitable arrangement of terminal switches on the two driven axes of the suspension arrangement, when a predetermined pivot angle of the working means relative to the fork or to the axis of the tapered or conical roller bearing is attained, the working means can be pivoted by means of corresponding drive means back into its starting position. Thus, for example, the position of the working means can serve as a starting position in which a beneficial guiding of the supply tubes and conduits to the working means, for example to a blasting or spray tool, is allowed. Also, position detectors can be arranged on both axes of the suspension device, especially angle detectors, which transmit to a control unit a response message regarding the positions of the two axes and with that, information regarding the alignment of the working means in relation to the surface to be worked. Thus, it can be guaranteed that the contact and engagement force engaging on the suspension arrangement works essentially only in one direction, which forms a right angle with the surface to be worked. The surface clamped by the fork of the suspension device is preferably parallel to the surface to be worked or forms an acute angle of 0 to 30xc2x0 with this surface.
A pneumatic or hydraulic cylinder, or a spring with a comparatively low spring stiffliess or force constant adapted to a specific work range or some similar arrangement can be considered as means for supplying the contact and engagement force. A hydraulic cylinder is operable alone or in cooperation with a hydraulic accumulator. Preferably it is operable with a constant and relatively low pressure. With use of a pneumatic cylinder, the accumulator effect can be attained particularly simply on the basis of the compressibility of the working medium. The distance modifications occurring during operation of the working means along a predeterminable path on the surface to be worked are compensated or equalized by means of raising the means for providing the contact and engagement force, especially the means in the form of the pneumatic cylinder. Several position switches can be arranged along the lifting path, especially at the end positions as well as in a central position. Instead of or alternatively to the position switches, which realize discrete position detection, a continuous position detection of the lifting position of the accumulator can also be provided.
The working means or the suspension device carrying the working means can be controlled in its rotation around two perpendiculars axes by a first driving means relative to the end of the working means adjacent to the overhang beam. Particularly, a first drive element of the first driving means rotates the suspension device around a first vertical axis and a second drive element of the first driving means rotates the suspension device around a first horizontal axis. Beyond that, the first drive element can additionally be configured to be rotatable around another horizontal axis by a third drive element of the first driving means. The first driving means serve for the follow-up or resettingxe2x80x94hereinafter to be referred to exclusively as resettingxe2x80x94of the means for supplying the contact and engagement force and are controlled from the position information coming from the means for providing the contact and engagement force. As a result of the pivot capacity of the working means in relation to the overhang beam, both the side working and the overhead working of the surface is possible. In turn, modifications of the distance between the working means and the surface to be worked are compensated or equalized by the means for providing the contact and engagement force.
Beyond that provision, the resetting of the means for supplying the contact and engagement force and with that the working means of the suspension device is thus executed by means of second driving means. The second driving means drive an overhang beam which can be displaced in and out telescopically, which in relation to the upper carrying chassis can be rotated around a second horizontal axis, and drive the upper carrying chassis in relation to a substructure or foundation, especially an undercarriage, rotatably around a second vertical axis.
The second driving means are thus at least partially controllable by the position information coming from the means for providing the contact and engagement force. Thus, for example, more or less simultaneously with the side blasting, by control of the in and out displacement of the overhang beam and of the rotation of the overhang beam around the second horizontal axis in relation to the upper carrying chassis, a path predeterminable by means of a control device can be covered on the surface to be worked. If, because of a curvature of the surface to be worked, the distance between the working means on the end of the overhang beam and the surface to be worked is so great that the distance can no longer be compensated by the means for providing the contact and engagement force, and with corresponding position information being transmitted from these means to the control device, for example, as a result of the operation of a terminal position switch, then the overhang beam is reset by rotation of the upper carrying chassis in relation to the substructure in the direction toward the surface to be worked, thereby equalizing the distance differential.
In a corresponding manner, in terms of the overhead blasting, a resetting can be executed by rotation of the overhang beam around the second horizontal axis, when the predetermined path has been covered by means of control of the in and out displacement of the overhang beam and by rotation of the upper carrying chassis in relation to the substructure. The displacements originating from the second driving means are thus detected by sensors, is especially, the resetting displacement is used as input variable for control of the displacement of the working means along the predetermined path, in order, for example, to be able by the resetting displacement to undertake certain control corrections and/or in order to hold the path velocity constant during the working of the surface.
Both the first and second driving means can particularly include double-acting pneumatic or hydraulic cylinders.
Such devices, insofar as they include a blasting tool, for example a tool for the working of ship hulls, especially the working of welded seams, can also be used for the removal of varnish or paint and other layers or pollutants or contaminants from aircraft. The provision of two outlet drains arranged offset from one another by 90xc2x0 guarantees reliable discharge of the waste materials arising from the working of the surface, both in the case of side blasting jets and also in the case of overhead blasting jets.
Side blasting operations, in which the surface to be worked forms an angle of, for example, 90xc2x0 to 45xc2x0 with the ground surface of the device, are executed essentially by in and out displacement of the overhang beam and by control of the rotary movement of the overhead beam in relation to the upper carrying chassis. Generally, the movements are powered hydraulically or else electrically. An overhead blasting, during which the surface to be worked includes an angle of, for example, 45xc2x0 to 0xc2x0 with the ground surface of the device, is essentially carried out by means of in and out displacement of the overhang beam and by control of the rotary movement of the upper carrying chassis in relation to-the substructure, generally likewise powered hydraulically or electrically. With both types of blasting applications, the means for providing the contact and engagement force guarantee the follow-up or resetting of the working means, while also attaining the spacing or distance modifications.
With the method for the operation of a device according to the present invention, the working means are first of all set up to contact and be engaged on the surface to be worked, then are displaced along the surface along a predeterminable path on the surface. The modifications of distances between the working means and the surface arising during the displacement along the path are compensated by the means for providing the contact and engagement force. The movement along the predeterminable path generally occurs by in and out displacement of the overhang beam and by rotation of said overhang beam around a second horizontal axis in relation to the upper carrying chassis, or else by rotation of the upper carrying chassis around a second vertical axis in relation to the substructure. These displacements are controlled, for example, by a stored-programmable control, whereupon automatized paths can be covered as desired. For example, meandering paths are offset one from the other and running essentially vertically. Overlapping paths are used for the clearing off and cleaning of an extended surface, for example a ship""s hull. The stored-programmable digital control does not undertake a direct control function for the contact of the working means on the surface to be worked. This is accomplished by the suspension of the working means, especially in connection with the accumulator of the means for providing the contact and engagement force. Even in the case of a curved surface, a continuous, consistent contact of the working means is guaranteed, without the necessity of knowing the precise shape of the curved surface beforehand, and especially without the necessity of describing the curved surface mathematically beforehand. The contact and engagement force is preferably provided by a pneumatic cylinder. As soon as the pneumatic cylinder reaches one end of its displacement path, and a corresponding terminal switch is operated, or a continuous position monitoring arrangement signals that the end position has been reached, the means for supplying a contact and engagement force are reset by means of the first and/or second driving means.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.